During the course of the life of a gas well, there are occasions when the formation starts producing significant amounts of liquid, most commonly water. The production of liquids can reduce the volume of gas produced. Depending on the formation pressure, the presence of liquid may result in an inability to push the produced fluids to the surface. At times the formation pressure can be low enough where only the less dense gas can be pushed to the surface with formation pressure. However, if the more dense liquid is present in sufficient quantities, then the formation pressure can be insufficient causing a reduction in gas production or the need to use artificial techniques to bring the production to the surface.
One solution that has been used is to use a downhole separator in conjunction with a submersible pump to actually produce the gas and liquids and separate them downhole so that the liquids can then be pumped to the surface for removal. This technique is illustrated in U.S. Pat. Nos. 6,736,880; 4,231,767 and 6,691,781. These solutions are complicated to execute because space is needed for auxiliary equipment as well as power being needed to drive the submersible pump. The present invention seeks an alternative to these traditional solutions by creating a device that preferentially lets the gas get produced while keeping the denser and more viscous water and other liquids from entering the production string. This is to be distinguished from techniques that provide varying resistance to production flow such as in a long horizontal run so as to avoid short circuiting into the production string at locations closer to the surface than more remote locations. One example of such a system is in US Application 2006/0272814 A1.
The present invention uses the difference in physical properties between gases and liquids to preferentially allow the gas to pass while reducing the liquid component of the incoming flow. In conjunction with an overlaying screen as an option, an annular space is provided between the screen and a base pipe where a flow resistance member is installed. The flow resistance member provides virtually little resistance to gas flow as compared to liquids and as a result reduces the amount of liquid passing through the annular area that reaches an opening in the base pipe. These and other advantages of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawing while recognizing that the full scope of the invention is to be found in the claims.